Friction generator



Patented Oct. 23, 1951 UNITED STATES PATENT OFFICE 2,572,765 FR'ICTION GENERATOR Jean Roudaut, New York, N. Y., assignor to Ghatham Electronics Corporation, Newark, N. J a corporation of New Jersey Application March 3, 1950, Serial No. 147,492

11 Claims. 1

This invention relates to friction generators, and has particular reference to generators which reverse their polarity when the direction of rotation is reversed.

Friction generators are quite old in the art of generation of electricity and were among the first mechanical appliances to be used in connection with the early experiments on electrical phenomena. Some of the first generators used a sphere of sulphur rubbing against a cloth. Others used ebonite and glass in various forms rubbing against pads of silk, leather and felt. One of the most eific'ient friction generators used a rotating glass disk with leather pads pressing against the disk surface. An amalgam of tin was spread on the leather surface to increase the available current.

All the above generators produced electricity of a predetermined polarit which was not dependent upon the direction of rotation of the moving member. Such generators were employed to demonstrate physical phenomena, generally in the class room, and had little or no practical application. However, during recent years, small high voltage generators have been used to charge instruments used for the detection and measurement of nuclear radiation. In this connection it is necessary to charge the instrument to a definite voltage, and if an overcharge is inadvertently applied, the instrument must be discharged and the process repeated.

One of the objects of this invention is to provide an improved friction generator which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to provide an electrostatic friction generator which changes polarity when the direction of rotation is changed.

Still another object of the invention is to provide a generator small in size and inexpensive to manufacture for charging measuring instruments and for giving the initial charge to influence-type high voltage generators.

The friction generator includes a rotor of insulating material made in the form of a flat disk. Resiliently pressed against one edge of the disk is a pad of fibrous material such as cotton. Adjacent to the pad, in rotary alignment, is one of the two brushes which are connected to the output terminals of the generator. The second brush is positioned in a similar manner but on the other side of the pad. Some means is provided for turning the rotor, either by hand or by some mechanical means. Provision must be made to turn the rotor in both directions if reversed polarity is desired.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

Fig. 1 is a schematic representation of a conventional prior art generator in which the rubbing pad is one of the electrodes.

Fig. 2 is a schematic representation of the reversible friction generator showin only the essential components.

Fig. 3 is a cross sectional view of one form of the friction generator, the section being taken vertically through the center of the rotor.

Fig. 4 is another cross sectional view of the generator shown in Fig. 3 taken along line 4-4 of that figure.

Referring now to Fig. 1, a prior art generator is shown to illustrate the improvements and differences between the known types of machines and the present invention. The generator comprises a rotor H), which in this example is a fiat disk, rotatable about a shaft l I. A friction pad I 2 is resiliently held against the rotor I0 and when the rotor is turned, electrical charges are created on the edge of the insulated disk due to the rubbing action. The charges may be taken off by a brush l3 which may touch the disk surface in generators which develop low voltages. In generators which develop a voltage exceeding 5,000 volts or more a spray brush, comprising a plurality of fine sharp points, may be used without making actual contact with the rotor surface.

One of the generator terminals [4 is connected to the friction pad 12 which may be positive or negative, depending upon the materials used. The second terminal [5 is connected to the brush I3.

Due to the symmetrical nature of the structure, it will be obvious that a change in direction of the rotor will have no effect on the polarity of the generated voltage.

Fig. 2 illustrates a schematic representation of the invention. Here a pad 12 is resiliently held against a rotating disk I 5) made of insulating material such as methyl-methacrylate rotatably mounted on shaft II. The pad I 2, however, is not one of the electrodes. One electrode is a spring pressed conductor is which is connected to an output terminal i1 and makes resilient contact with the rotor !0 at a point close to one side of the friction pad l2. The second electrode 3 is a similar spring pressed conductor connected to a When either one or both brushes is positioned a considerable distance from the pad there isa noticeable time lag when the polarity of the voltage is reversed and the rotor is turned slowly by hand. For this reason, and for other reasons involving mechanical design, the brushes are generally positioned as indicated by Fig. 2

When the rotor in the above described generator is made of methyl-methacrylate and the pad comprises a thick wad of cotton, a voltage of about 10,000 volts is generated between the terminals ll2ll when the shaft l I is rotated about two revolutions per second. If the shaft and rotor are turned in the counterclockwise direction as viewed in Fig. 2, terminal 20 will become positive and terminal 1! will be negative. Reversal of the direction of rotation reverses the polarity of the terminals. The accumulated charges which are collected by brushes it and I6 may be used tocharge a condnser, charge a radiation dosimeter, or slowly discharge through a connected resistor 2|, in which case the generator may be classified as a direct current generator.

Figs. 3 and 4 illustrate the manner in which the reversible generator may be made into a small manually driven machine to charge an instrument for detection of nuclear radiation. A case comprising non-conducting side walls 22 and 23 encloses the rotor It on shaft ll driven by a knurled knob 26. Spacers 24 keep the rotor in alignment. A cotton pad is resiliently held against the edge of rotor l by a spring 25. In this example the electrodes are held against the rotor edge by helical springs 27 and 28.

It has been found by experiment that if cotton is used as the material for the friction pad l2 and if methyl-methacrylate is used as the rotor, the generator works best when the surrounding air has a humidity of about fifty percent. It has also been found that friction pads of fibroussilk, wool, glass, and nylon have similar characteristics. While these materials work well for all ordinary applications, they obviously fail when the temperature is lowered below degrees centigrade since under these conditions the humidity is too low to permit the pads to function properly. a

The above pad materials are all characterized by a chemical group which includes NH2,.OH,

" COOI-I, or other hydrophile structures and have a certain affinity to water. In order to produce a generator that would not be affected by humidity many substances were tested and it was discovered that a group of halogenated hydrocarbons (plastics) could be used in a perfectly dry atmosphere and could also withstand temperatures of +70 degrees to 70 degrees centigrade without aifecting their electrical properties. Some of these substances are polyvinyl chloride, tetrafluoroethylene (teflon), and trifluorochloroethylene. The use of these materials as friction pads does not change the polarity of the generated charges when employed in conjunction with a rotor of methyl-methacrylate (Lucite) or polystyrene.

v When a manually operated generator is used to charge a radiation sensitive instrument, the knob 26 is turned slowly in one direction while observing the charge indicator. When the indicator shows that the required charge has been applied the motion is stopped and the generator disconnected. If an overcharge is inadvertently applied it is only necessary to turn the rotor in the opposite direction to reduce the charge to the correct amount.

While there have been described and illustrated specific embodiments of the invention, it will be obvious that various changes and modifications may be made therein without departing from the field of the invention which should be limited only by the scope of the appended claims.

I claim:

l. A friction generator comprising, a rotor made of insulating material, a pad resiliently pressed into contact with the rotor, two brushes for conducting generated electrical charges to output terminals, said brushes comprising conductors in contact with the "rotor on either side of said pad, and means for turning the rotor in either direction.

2. A friction generator comprising, a rotor made of insulating material, a pad resiliently pressed into contact withthe rotor, two brushes for conducting generated electrical charges to output terminals, said brushes comprising conductors in contact with the rotor on either side of the pad, and means for turning the rotor in either direction to provide electrical potentials at the output terminals, the polarity of which depends upon the direction of rotation of the rotor.

3. A friction generator comprising, a rotor made of insulating material in the form of a flat disk, a pad resiliently pressed into contact with the rotor disk, two brushes for collecting generated electrical charges and making them available to a load circuit, said brushes comprising conductors in contact with the rotor on either side of the pad, and means for turning the rotor in either direction to provide electrical potentials at the brushes, the polarity of which depends upon the direction of rotation of the rotor.

4. A friction generator comprising, a rotor made of insulating material in the form of a fiat disk mounted for rotation, a pad having a fibrous structure resiliently pressed into contact with the rotor disk, two brushes for collecting generated electrical charges and making them available to a load circuit, said brushes comprising conductors in contact with the rotor on either side of the pad, and means for turning the rotor in either direction to provide electrical potentials at the brushes, the polarity of which depends upon the direction of rotation of the rotor.

5. A friction generator comprising, a rotor made of insulating material in the form of a fiat disk mounted for rotation, a pad having a fibrous structure resiliently pressed into contact with the rotor disk, two brushes for collecting generated electrical charges and making them available to a load circuit, said brushes comprising conductors in resilient contact with the rotor adjacent to the pad and on either side thereof in rotation alignment, and means for turning the rotor in either direction to provide electrical potentials at the brushes, the polarity of which depends upon the direction of rotation of the rotor.

6. A friction generator comprising, a base member for securing non-rotating components, a rotor made of insulating material in the form or a fiat disk and rotatably mounted on said base, a pad mounted on the base and resiliently pressed into contact with the rotor disk, two brushes also mounted on the base for collecting generated electrical charges and making them available to a load circuit, said brushes comprising conductors in contact with the rotor on either side of the pad, and means for turning the rotor in either direction to provide electrical potentials at the brushes, the polarity of which depends upon the direction of rotation of the rotor.

7. A friction generator comprising, a base member for securing non-rotating components, a rotor made of insulating material in the form of a fiat disk and rotatably mounted on said base, a pad having a fibrous structure mounted on the base and resiliently pressed into contact with the rotor disk, two brushes also mounted on the base for collecting generated electrical charges and making them available to a load circuit, said brushes comprising metallic conductors in resilient contact with the rotor adjacent to the pad and on either side thereof in rotation alignment, and means for turning the rotor in either direction to provide electrical potentials at the brushes, the polarity of which depends upon the direction of rotation of the rotor.

8. A friction generator comprising, a rotor made of methyl-methacrylate, a pad of halogenated hydrocarbon plastic in fibrous form resiliently pressed into contact with the rotor, two brushes for collecting generated electrical charges, said brushes comprising conductors in contact with the rotor on either side of said pad, and means for turning the rotor in either direction.

9. A friction generator comprising, a rotor made of methyl-methacrylate, a pad of halogenated hydrocarbon plastic in fibrous form resiliently pressed into contact with the rotor,

two brushes for collecting generated electrical charges, said brushes comprising conductors in contact with the rotor on either side of the pad, and means for turning the rotor in either direction to provide electrical potentials at the output terminals, the polarity of which depends upon the direction of rotation of the rotor.

10. A friction generator comprising, a rotor made of an inert hydrocarbon plastic in the form of a flat disk, a pad of halogenated hydrocarbon plastic in fibrous form resiliently pressed into contact with the rotor disk, two brushes for collecting generated electrical charges and making them available to a load circuit, said brushes comprising conductors in contact with the rotor on either side of the pad, and means for turning the rotor in either direction to provide electrical potentials at the output terminals, the polarity of which depends upon the direction of rotation of the rotor.

11. A friction generator comprising, a base member for securing non-rotating components, a. rotor made of an inert hydrocarbon plastic in the form of a flat disk and rotatably mounted on said base, a pad of halogenated hydrocarbon plastic in fibrous form mounted on the base and resiliently pressed into contact with the rotor disk, two brushes also mounted on the base for collecting generated electrical charges and making them available to a load circuit, said brushes comprising conductor in contact with the rotor on either side of the pad, and means for turning the rotor in either direction to provide electrical potentials at the output terminals, the polarity of which depends upon the direction of rotation of the rotor.

JEAN ROUDAUT.

No references cited. 

1. A FRICTION GENERATOR COMPRISING, A ROTOR MADE OF INSULATING MATERIAL, A PAD RESILIENTLY PRESSED INTO CONTACT WITH THE ROTOR, TWO BRUSHES FOR CONDUCTING GENERATED ELECTRICAL CHARGES TO OUTPUT TERMINALS, SAID BRUSHES COMPRISING CONDUCTORS IN CONTACT WITH THE ROTOR ON EITHER SIDE OF SAID PAD, AND MEANS FOR TURNING THE ROTOR IN EITHER DIRECTION.
 8. A FRICTION GENERATOR COMPRISING, A ROTOR MADE OF METHYL-METHACRYLATE, A PAD OF HALOGENATED HYDROCARBON PLASTIC IN FIBROUS FORM RESILIENTLY PRESSED INTO CONTACT WITH- THE ROTOR, TWO BRUSHES FOR COLLECTING GENERATED ELECTRICAL CHARGES, SAID BRUSHES COMPRISING CONDUCTORS IN CONTACT WITH THE ROTOR ON EITHER SIDE OF SAID PAD, AND MEANS FOR TURNING THE ROTOR IN EITHER DIRECTION. 